The present invention relates to a saw chain tensioner for imparting a suitable level of tension to the saw chain of a chain saw.
A known saw chain tensioner has a threaded rod member rotatably received in a hole in the frame of a chain saw, a clip or a special lock nut fixed to the threaded rod so as to prevent the threaded rod from coming off the chain saw frame when the threaded rod is moved axially as a result of rotation, and a pin member screwed onto the threaded portion of the threaded rod member and having a portion which is extended through a lateral guide slot formed in a side plate which is disposed between a chain guide bar and the chain saw frame, the portion being further extended into a slot formed in the chain guide bar. As the threaded rod member is rotated, the pin member is moved back and forth in the axial direction of the threaded rod member so as to displace the chain guide bar in the longitudinal direction thereof, whereby the span of the saw chain is adjusted to control the level of the tension applied to the saw chain.
This type of saw chain tensioner is disadvantageous in that the production cost of the chain saw is raised and the repair or maintenance work is made difficult due to the provision of a clip or a lock nut which is attached to the threaded rod for the purpose of preventing the threaded rod from coming off the frame of the chain saw.